Just as Ford is edging away from hybrid cars in the U.S., Japanese automakers continue to be less, ahem, fuelish. Motivated by the high cost of fuel in Japan and tough emission standards, among other factors, Mitsubishi Fuso this week unveiled the most energy-efficient medium-duty truck in the world, the Canter Eco Hybrid. With its diesel-electric drivetrain, the Canter offers the best of both worlds: a Li-ion-powered electric motor that kicks into action during stop-and-go driving (ideal for city-bound, delivery-type trucks like this), and a high-efficiency, cleaner-burning diesel engine for highway cruising (which, of course, can always be powered by some good ol' biodiesel). The truck also shuts off its engine while idling, and includes a regenerative braking system that "recycles" energy expended when the truck slows down into electrical energy for later use (here's a diagram of the truck's different operating modes). The result is a 20 percent improvement in fuel efficiency over similar trucks, and the first commercial truck to meet Japan’s new long-term emissions regulations, due to come into effect August 2007.Because of the relative efficiency of modern (bio) diesel engines compared with petrol engines, diesel hybrids are becoming a popular, if still more costly twist on typical hybrid cars (some have shown that non-hybrid diesel engines can prove more fuel efficient and less polluting than conventional hybrids, as Green Car Congress does in a 2004 study ). DaimlerChrysler (which largely owns Mitsubishi Fuso) is betting on hybrid diesel in a big way for trucks and buses while GM has talked up a diesel hybrid passenger sedan, the Opel Astra, which may go into production in 2007. In the meantime, we can breathe a little easier knowing that diesel hybrid buses are proliferating around Europe, Asia, and the U.S., that FedEx is already driving some diesel hybrids in the States, that innovative diesel hybrid UPS trucks are on their way, that sweet cars like this and this are being dreamed up, and that, if Mitsubishi sees enough interest outside of Japan, the Fuso might soon be delivering packages in our hometown too.